<html>
<head>
	<meta charset="UTF-8">
	<meta content="IE=edge" http-equiv="X-UA-Compatible">
	<meta content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no, width=device-width" name="viewport">
	<title>2692：表达式计数</title>
	<!-- css -->
	<link href="../css/base.min.css" rel="stylesheet">
	<link href="../css/project.min.css" rel="stylesheet">
	
	<!-- favicon -->
	<!-- ... -->
</head>
<body class="page-brand">
	<header class="header header-transparent header-waterfall ui-header">
		<ul class="nav nav-list pull-left">
			<li>
				<a data-toggle="menu" href="#menu">
					<span class="icon icon-lg">menu</span>
				</a>
			</li>
		</ul>
		<a class="header-logo header-affix-hide margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">表达式计数</a>
		<span class="header-logo header-affix margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">表达式计数</span>
	</header>
	<nav aria-hidden="true" class="menu" id="menu" tabindex="-1">
		<div class="menu-scroll">
			<div class="menu-content">
				<a class="menu-logo" href="../index.html">BZOJ离线题库</a>
				<ul class="nav">
					<li>
						<a class="waves-attach" data-toggle="collapse" href="#problems">题目</a>
						<ul class="menu-collapse collapse in" id="problems">
							<li>
								<a class="waves-attach" href="../index.html">主页</a>
							</li>
							<li>
								<a class="waves-attach" href="../list.html">题目列表</a>
							</li>
						</ul>
					</li>
					<li>
						<a class="collapsed waves-attach" data-toggle="collapse" href="#about">关于</a>
						<ul class="menu-collapse collapse" id="about">
							<li>
								<a class="waves-attach" href="../about.html">关于此项目</a>
							</li>
						</ul>
					</li>
					
				</ul>
			</div>
		</div>
	</nav>
	<main class="content">
		<div class="content-header ui-content-header">
			<div class="container">
				<h1 class="content-heading">
                表达式计数                </h1>
                <p>时间限制：20s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
		</div>
		<div class="container">
			<section class="content-inner margin-top-no">
				<div class="row">
					<div class="col-lg-13 col-md-13">
						<div class="card margin-bottom-no">
							<div class="card-main">
								<div class="card-inner">
									
                                <h3>题目描述</h3><p><div id="ptit" class="probtitle" style="text-align: center; padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; font-family: 微软雅黑, 黑体, 'Times New Roman'; font-size: 24pt; font-weight: bold; padding-top: 0px"><span style="font-size: medium"><br />
</span></div>
<div id="pcont1" style="text-align: left; padding-bottom: 0px; margin: 20px 0px 0px; padding-left: 0px; padding-right: 0px; font-family: 宋体, 'Times New Roman'; padding-top: 0px">
<div class="pdcont" style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; font-family: 'Times New Roman', 宋体; color: rgb(32,0,0); font-size: 14px; padding-top: 0px"><span style="font-size: medium">　　Answer的数学太差了，他决定恶补一番。<br style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px" />
不过在学其他东西之前，他必须先精通加减乘除四则运算。<br style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px" />
他想知道对于N个变量，每个变量只能用一次，且不能有前导符号，在可以使用括号的基础上，有多少种本质不同的运算方案？由于答案会很大，所以只需要输出模1000000007之后的答案。<br style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px" />
两个方案本质相同即，无论如何改变这些变量的值，两种方案的结果不变(当然，要在表达式有意义的基础上)<br style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px" />
例如:a/b/c和a/(b*c)的本质是相同的。<br style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px" />
</span></div>
<div class="pdsec" style="border-bottom: rgb(187,187,187) 1px solid; padding-bottom: 4px; background-color: rgb(248,248,255); margin: 8px 0px 4px; padding-left: 6px; padding-right: 0px; font-family: 微软雅黑, 黑体, 华文细黑; font-weight: bold; padding-top: 4px; border-top-left-radius: 4px; border-top-right-radius: 4px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px"><br />
<font size="3"><br />
</font></div>
</div>
<p></p></p><hr/><h3>输入格式</h3><p><p></p>
<div></div>
<div>
<div id="pcont1" style="text-align: left; padding-bottom: 0px; margin: 20px 0px 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px">
<div class="pdcont" style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; font-family: 'Times New Roman', 宋体; color: rgb(32,0,0); font-size: 14px; padding-top: 0px"><span style="font-size: medium">　　输入的第一行包含一个正整数Test表示数据组数。<br style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px" />
以下Test行，每行表示一个询问N,询问N个变量的本质不同的表达式方案。<br style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; padding-top: 0px" />
</span></div>
<div class="pdsec" style="border-bottom: rgb(187,187,187) 1px solid; padding-bottom: 4px; background-color: rgb(248,248,255); margin: 8px 0px 4px; padding-left: 6px; padding-right: 0px; font-weight: bold; padding-top: 4px; border-top-left-radius: 4px; border-top-right-radius: 4px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px"><font color="#200000" size="3" face="'Times New Roman', 宋体"><br />
</font></div>
</div>
</div></p><hr/><h3>输出格式</h3><p><div class="pdsec" style="border-bottom: rgb(187,187,187) 1px solid; text-align: left; padding-bottom: 4px; background-color: rgb(248,248,255); margin: 8px 0px 4px; padding-left: 6px; padding-right: 0px; font-family: 微软雅黑, 黑体, 华文细黑; font-size: 16px; font-weight: bold; padding-top: 4px; border-top-left-radius: 4px; border-top-right-radius: 4px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px"><span style="font-family: 'Times New Roman', 宋体; color: rgb(32,0,0); font-size: medium">　　输出一个非负整数，表示方案数模1000000007后的值。</span></div>
<div class="pddata" style="text-align: left; padding-bottom: 0px; margin: 0px; padding-left: 24pt; padding-right: 0px; font-family: 'Courier New', FixedSys; color: rgb(32,0,0); padding-top: 0px"><font size="3"><br />
</font></div>
<p></p></p><hr/><h3>样例输入</h3><pre>2
1
2
</pre><hr/><h3>样例输出</h3><pre>1
6
</pre><hr/><h3>提示</h3><p><div>样例说明</div>
<div>　　对于N=2,有a+b,a-b,b-a,a*b,a/b,b/a六种方案。</div>
<div>数据规模和约定</div>
<div>　　对于30%的数据，满足1&le;N&le;50</div>
<div>　　对于100%的数据,满足1&le;N&le;2000,1&le;Test&le;2000</div>
<div></div>
<p></p></p><hr/><h3>题目来源</h3><p>没有写明来源</p>
								</div>
							</div>
						</div>
					</div>
				</div>
				
				
			</section>
		</div>
	</main>

	<div class="fbtn-container">
		<div class="fbtn-inner">
			<a class="fbtn fbtn-lg fbtn-brand-accent waves-attach waves-circle waves-light waves-effect" data-toggle="dropdown" aria-expanded="true"><span class="fbtn-text fbtn-text-left">Menu</span><span class="fbtn-ori icon">apps</span><span class="fbtn-sub icon">close</span></a>
			<div class="fbtn-dropup">
				<a class="fbtn fbtn-brand waves-attach waves-circle waves-light waves-effect" href="../list.html" target="_self"><span class="fbtn-text fbtn-text-left">题目列表</span><span class="icon">menu</span></a>
				<a class="fbtn fbtn-green waves-attach waves-circle waves-effect" href="../index.html" target="_self"><span class="fbtn-text fbtn-text-left">返回主页</span><span class="icon">home</span></a>
				<a class="fbtn waves-attach waves-circle waves-effect" href="http://www.lydsy.com/JudgeOnline/submitpage.php?id=2692" target="_blank"><span class="fbtn-text fbtn-text-left">提交代码</span><span class="icon">send</span></a>
				<a class="fbtn fbtn-orange waves-attach waves-circle waves-effect" href="http://www.lydsy.com/JudgeOnline/wttl/wttl.php?pid=2692" target="_blank"><span class="fbtn-text fbtn-text-left">试题讨论</span><span class="icon">chat</span></a>
				
			</div>
		</div>
	</div>

	<!-- js -->
	<script src="../js/jquery.min.js"></script>
	<script src="../js/base.min.js"></script>
	<script src="../js/project.min.js"></script>
</body>
</html>